The building, behind the Tower of London, has been earmarked to become a hotel for at least seven years but none of the plans has come to fruition.

Mr Thomas's company, Thomas Enterprises, bought the site in September 2006 from insurance firm Willis for £100million. It has now applied to the City Corporation for planning permission to go ahead with the hotel.

Rob Steul of architects Woods Bagot, designer of the proposed scheme, said: "Our vision for 10 Trinity is to create the finest hotel in London and restore one of its most important Grade II*-listed buildings. There is no other site like this in the capital, which offers a position near the City and Canary Wharf, while overlooking a World Heritage site at the Tower of London.

"We have been working with English Heritage and the City to develop a design which removes unsympathetic Sixties extensions and restores the central rotunda space to the building, which was lost during the Blitz.

"The proposed new extensions blend the listed building with a modern glass-domed extension in the courtyard. This immense 30-metre diameter central space will become the new heart of the building, and rival the scale of the Great Court of the British Museum."

Designed by Sir Edwin Cooper, 10 Trinity Square was built between 1915 and 1922 and was originally the headquarters of the Port of London Authority. Part of its main design was its decorative roof "rotunda" feature, once described as a "wedding cake".

The building hosted the inaugural reception of the General Assembly of the United Nations in 1946. In February 2002 it was nearly sold for £60million to Development Securities, which had the same idea of turning it into a hotel, but the deal fell through. Woods Bagot converted the Trafalgar Square Hilton and the Courthouse Doubletree at Great Marlborough Street and is behind the extension to the Grosvenor House hotel.

Chris Rouse, director of CB Richard Ellis Hotels, said: "The increase in applications for change of use from offices to hotels is a product of the general 'softening' in the office development market. But it also reflects a sense of optimism for hotel development that has been engendered by the 2012 Olympics."

Mr Thomas started his real estate company in the early Eighties in Georgia and struggled to build up Thomas Enterprises over the next decade.

But the firm gradually spread through Carolina, Florida, Kentucky, Alabama and Georgia with almost 10 million sqft of retail space.

In the mid-Nineties Mr Thomas created an internal brokerage arm which allowed the company to spread further afield. It has now developed more than 40 million sq ft of retail property valued at $4billion (£2.8billion). It also owns more than 20,000 acres of land in America.